Heynckes replaced Jurgen Klinsmann on Monday after the 44-year-old was sacked following Bayern's 1-0 home defeat by Schalke 04. They are third in the league, three points off the top with five matches left.
Bayern are already out of the German Cup and the Champions League and failing to finish in the top two, missing automatic qualification to the top European competition, could spell financial disaster for the club.
"The aim must be direct qualification for the Champions League. I can help with my experience and my know-how in this present situation," Heynckes said.
"We should not think about the title, let alone talk about it," Heynckes, 63, who coached Bayern from 1987 to 1991, winning two championships, told the club's website.
"Bayern mean a lot to me. I am confident it will work," Heynckes said.
"This is obviously not a dream start. This is everything but comfortable," he said.
